River Engineering and the Environment

By: Meghan MoratzFolsom Dam, California (Source: How)

The Gavins Point Dam being built on the Missouri River in South Dakota. The dam controls the flow of everything downstream. In 2011, this dam released more than twice the record amount of water ever released, which caused severe flooding and shut down bridges throughout the Midwest. (Source: United)

Rivers have been channelized to control the flow around cities and to maximize the land available for development. (Source: United)

From 1890 to 1989 the watershed has changed drastically. This part of the lower Mississippi River has been channelized so agriculture could prosper along the river. Prior to channelization, the river had a wide path, marshes, and sand/mud banks. In addition, channelization greatly decreased the width of the river.(Source: United)

Revetments are used to straighten rivers and control their course to increase the land available for farming. (Source: Lowery)

In 1934 a dike system was put into the Missouri River along Indian Cave Bend. This series of photos shows how the dikes forcibly narrowed the river and destroyed aquatic species’ habitat. (Source: United)

Before the Great Floods of 1993 the rivers were very narrow due to river engineering. But during the floods, the river overflowed its banks and into its natural floodplain.(Source: United)

When rivers are engineered the regular flooding periods can become more destructive, which causes bridges to be destroyed by the increased velocity of water. (Source: Marx)

Farms were flooded during the Great Mississippi River Flood of 1927, while flooding is disastrous for people, it benefits the soil and is what made the soil near waterways so fertile. Dams prevent smaller, regular floods, but create larger, much more disastrous floods, for example, along the Missouri River in 2011. (Source: United)

Fertilizer runoff from farms is a huge source of the nitrogen that causes hypoxia in the Gulf of Mexico. The runoff also erodes the shorelines of rivers, making revetments necessary to maintain the land area for the people to use. (Source: Eutrophication)

Algal blooms and red tides are common in the Gulf of Mexico’s dead zone. Runoff from farms upstream accumulate and all the nitrogen is dumped into the Gulf. (Source: Genesio)

Nitrogen is put into the watersheds all over the Midwestern United States, and it accumulates as it flows downstream, resulting in more than 90% of all Nitrogen in the Gulf of Mexico dead zone. (Source: United)

Bass are native to the Missouri River, but when species like carp are introduced,

the bass’ habitat is destroyed.

Carp eat plankton in the sediment and

leave the water very turbid.

Plants cannot grow in turbid water as they need sunlight, and bass need the plants to

provide a habitat for

them. (Source: Moratz)

Paddlefish are also affected by carp, because they compete for the same food resources and carp tend to outcompete paddlefish. (Source: Moratz)

Bighead carp are introduced species that outcompete native fish because they grow and reproduce much faster than fish, like paddlefish. (Source: Moratz)

Fish spawn upstream, as shown above, when a dam is built fish cannot get to their upstream spawning grounds. (Source: Mitchell)

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Blog. N.p., n.d. Web."How Do Dams Work?" USSD. United States Society on Dams, n.d. Web.Lowery, Ron. Farms Along Missouri River. N.d. Photograph. Grain Valley,

Missouri.Marx, Groucho K. "Capt. Spaulding's World." : "Historic" Levels of Missouri

River Reservoirs Mean Flooding. N.p., n.d. Web.Mitchell, Jeff J. "Salmon Return Upstream From The Atlantic To Spawn In

Scottish Rivers." Zimbio. Getty Images Europe, n.d. Web.Moratz, Collin. Fish. 2012. Photograph. Missouri RiverUnited States. Department of the Interior. Geological Survey. A Brief History

and Summary of the Effects of River Engineering and Dams on the Mississippi River System and Delta. By Jason S. Alexander, Richard

C. Wilson, and W. Reed Green. Quick Search. Web